Applied Surface Science, Vol.427, 1105-1113, 2018
Derivative effect of laser cladding on interface stability of YSZ@Ni coating on GH4169 alloy: An experimental and theoretical study
Yttria-stabilized zirconia YSZ@Ni core-shell nanoparticles were used to prepare a thermal barrier coating (TBC) on a GH4169 alloy by laser cladding. Microstructural analysis showed that the TBC was composed of two parts: a ceramic and a bonding layer. In places where the ZrO2/Al2O3 eutectic structure was present in the ceramic layer, the Ni atoms diffused into the bonding layer, as confirmed by energy-dispersive X-ray spectroscopy (EDS). The derivative effect of laser cladding results in the original YSZ@Ni core-shell nanoparticles being translated into the Al2O3 crystal, activating the YSZ. The mechanism of ceramic/metal interface cohesion was studied in depth via first-principles and molecular dynamics simulation. The results show that the trend in the diffusion coefficients of Ni, Fe, Al, and Ti is D-Ni > D-Fe > D-Ti > D-Al in the melting or solidification process of the material. The enthalpy of formation for Al2O3 is less than that of TiO2, resulting in a thermally grown oxide (TGO) Al2O3 phase transformation. With regard to the electronic structure, the trend in Mulliken population is Q(O-Ni) > Q(Zr-O) > Q(O-Al). Although the bonding is slightly weakened between ZrO2/Al2O3 (Q(Zr-O) = 0.158 < Q(O-Ni) = 0.220) compared to that in ZrO2/Ni, TGO Al2O3 can improve the oxidation resistance of the metal matrix. Thus, by comparing the connective and diffusive processes, our findings lay the groundwork for detailed and comprehensive studies of the laser cladding process for the production of composite materials. (C) 2017 Elsevier B.V. All rights reserved.
Keywords:YSZ@Ni nanoparticles;Thermal barrier coatings;Interface conjunction;Microcosmic mechanism;First-principles